Process for producing 1,1,1-trichloroethane

ABSTRACT

A process for the separation of 1,1-dichloroethane from cis- and trans-1,2-dichloroethylene by the direct distillation of the trans-1,2-dichloroethylene, which boils approximately 10* lower than the 1,1-dichloroethane and cis-1,2-dichloroethylene, away from the latter two and the subsequent isomerization of the cis1,2-dichloroethylene, at a temperature approximately 500*C, to establish an equilibrium mixture of cis- and trans-isomer. The resulting cis- and trans-isomer mixture is subjected to distillation and the separation of the trans- from the cis- and the recycle of the cis- to the isomerization step. This process has utility in the preparation of 1,1,1-trichloroethane from ethyl chloride. In such a process as the direct thermal chlorination of ethyl chloride to 1,1,1-trichloroethane there are produced numerous by-products, most of which are separable by simple distillation from the 1,1-dichloroethane. However, the cis-isomer boils so close to 1,1-dichloroethane that it is practically inseparable unless rigid purification techniques of distillation are employed. The process of the present invention provides a convenient method for the simple distillation of the single product trans-1,2-dichloroethylene from the mixture of cis-, trans- and intermediate 1,1-dichloroethane stream from a thermal chlorination of ethylchloride to 1,1,1-trichloroethane and permits the recycle of the 1,1-dichloroethane with such cisisomer to the reactor which operates under reaction conditions that the cis-isomer is isomerized to an equilibrium mixture with trans-isomer. The repeated recycling of the cis-isomer with the recycled 1,1-dichloroethane permits the thermal chlorination reactor to product 1,1,1-trichloroethane in high yields by preventing the cis- and trans-isomers of 1,2-dichloroethylene from building up to an unacceptable level in the recycled 1,1dichloroethane.

United States Patent [1 1 Willis et al.

[ PROCESS FOR PRODUCING 1,1,1-TRICHLOROETHANE [75] Inventors: Gordon G. Willis; John B. Ivy;

Theodore S. Boozalis; Darryl E. Cragar, all of Lake Jackson, Tex.

[73] Assignee: The Dow Chemical Company,

Midland, Mich.

[221 Filed: Apr. 22, 1974 [21] Appl. No.2 462,702

[52] US. Cl 260/658 R [51] Int. Cl. C07C 17/10 [58] Field of Search 260/654 R, 658 R, 654 H,

56 References Cited UNITED STATES PATENTS 3,012,081 12/1961 Conrad et al. 260/658 R 3,059,035 10/1962 Benner et a1 260/658 R Primary Examiner-Delbert E. Gantz Assistant Examiner.loseph A. Boska Attorney, Agent, or FirmGlwynn R. Baker [57] ABSTRACT A process for the separation of l,l-dichloroethane from cisand trans-l,2-dichloroethylene by the direct distillation of the trans-l,2-dichloroethylene, which boils approximately l0 lower than the l,ldichloroethane and cis-1,2-dichloroethylene, away from the latter two and the subsequent isomerization Dec. 16, 1975 of the cis-1,2-dichloroethylene, at a temperature approximately 500C, to establish an equilibrium mixture of cisand trans-isomer. The resulting cisand trans-isomer mixture is subjected to distillation and the separation of the transfrom the cisand the recycle of the cisto the isomerization step. This process has utility in the preparation of 1,1,l-trichloroethane from ethyl chloride. In such a process as the direct thermal chlorination of ethyl chloride to 1,1,1- trichloroethane there are produced numerous byproducts, most of which are separable by simple distillation from the 1,1 -dichloroethane. However, the cisisomer boils so close to l,l-dichloroethane that it is practically inseparable unless rigid purification techniques of distillation are employed. The process of the present invention provides a convenient method for the simple distillation of the single product trans-1,2- dichloroethylene from the mixture of cis-, transand intermediate l,l-dichloroethane stream from a thermal chlorination of ethylchloride to l,l,ltrichloroethane and permits the recycle of the l,ldichloroethane with such cis-isomer to the reactor which operates under reaction conditions that the cisisomer is isomerized to an equilibrium mixture with trans-isomer. The repeated recycling of the cis-isomer with the recycled l,l-dichloroethane permits the thermal chlorination reactor to product 1,1,1- trichloroethane in high yields by preventing the cisand trans-isomers of l,2-dichloroethylene from building up to an unacceptable level in the recycled l,ldichloroethane.

1 Claim, N0 Drawings PROCESS FOR PRODUCING 1,1,1-TRICI-ILOROETHANE BRIEF DESCRIPTION OF THE INVENTION The present invention employs a technique of simple distillation of transl,2-dichloroethylene from a mixture of cisand trans-1,2-dichloroethylene and 1,1- dichloroethane. The transisomerboils approximately 10 below .the boiling point of l,ldichloroethane and approximately 13 below the boiling point of the cisisomer; thus, upon the separation of the fraction containing both cisand trans-dichloroethylene and 1,1- dichloroethane from the product stream from the reactor there is obtained a mixture which is capable of separation of transisomer from the mixture. The resulting mixture of cis-1,2-dichloroethy1ene and 1,1- dichloroethane can then be recycled to a reactor wherein the temperature is in the range of approximately 400C to about 600C, and preferably about 500C. Under this condition of temperature and in the presence of the l,ldichloroethane, ethyl chloride and chlorine there is obtained an isomerization of the cisisomer to an equilibrium mixture of cisand transisomers. The resulting effluent of this reaction mixture, passed to a simple distillation column, separates the eflluent into several fractions of which of course there is obtained the cis-, transmixture with l,ldichloroethane. This three-component mixture can be separated by a fairly simple distillation column to produce transdichloroethylene and a mixture of cis-1,2-dichloroethylene and l,ldichloroethane. This resulting l,ldichloroethane and cis-l,2-dichloroethy1ene is recycled to the thermal chlorinator wherein the cis-isomer is isomerized and the l,ldichloroethane chlorinated, producing a useful product, 1,1,l-trichloroethane. The ethyl chloride which is fed to the thermal chlorinator along with this recycled l,ldichloroethane produces of course 1, l-dichloroethane in the effluent.

- therrnochlorination of ethyl chloride and the recycle of that so-produced l,ldichloroethane to the same thermal chlorination reactor there is simultaneously produced 1,1,l-trichloroethane and vinylidene chloride, very desirable products. The 1, l-dichloroethane which is produced by the chlorination of ethyl chloride in this reaction is not readily separable from impurities, primarily cisand trans-1,2-dichloroethylene. It is well known that 1,2-dich1oroethylene in the transform boils at approximately 10 lower than the 1,1- dichloroethane and thus is capable of separation in a still from a mixture of cisand trans-dichloroethane and l,ldichloroethane. If the trans-isomer is removed from the mixture of cisand trans-dichloroethylene and l,ldichloroethane, there is resulting a two-component mixture of 1 l-dichloroethane and cis-dichloroethylene which can be fed back to the thermochlorinator wherein the l,ldichloroethane is thermally chlorinated to 1,1 ,l-trichloroethane and vinylidene chloride. Under the conditions of the chlorination reaction, that is, in the presence of chlorine and at a temperature of above about 400C, the cisisomer will isomerize to an equilibrium mixture of approximately 60% cisisomer and 40% transisomer. Thus, it is apparent if the transisomer is removed from combination with the 1,1-

2 dichloroethane and cisisomer that upon recycle to the reactor the cisisomer being re-isomerized to the 60/40 mixture with the transthere results a continuous reduction in amount of transisomer from the system.

5 Such control of these isomers will effect favorably the reaction of l,ldichloroethane and ethyl chloride taking place in the chlorinating reactor and will markedly reduce the quantity of the cisand transisomers as well as reduce the amount of more highly chlorinated chlorohydrocarbon such as tetrachloroethane, perchloroethylene or trichloroethylene.

In the following example a synthetic mixture of chlorine, l,ldichloroethane, ethyl chloride and cisdichloroethylene along with HCl which would be the approximate feed from a commercial operation in which ethyl chloride and l,ldichloroethane are chlorinated and the l,ldichloroethane is recycled to produce in the same chlorination reactors, simultaneously with the chlorination of the ethyl chloride, l,l,l-trichloroethane and vinylidene chloride. The cisdichloroethane concentration of the feed component was altered from 0 to 2.1 moles per hour in an overall feed of approximately 52 to 54 total moles per hour. The reactor temperature and other reaction conditions are set forth below. The efiluent product from the chlorination reactor was separated into several fractions one of which was a trans-, cis-trichloroethylene fraction which contained the majority of the 1,1- dichloroethanes produced in the thermochlorination. This fraction was separated into cis and 1,1- dichloroethane and a trans-fraction which latter fraction was removed. The resulting mixture of cisand l,ldichloroethane were then recycled to the thermochlorinator. Thus, according to this process, employing the artificial feed, several examples were run in which the concentration of the cis-dichloroethylene was changed. In the tabular form below, the reactor conditions of the feed in moles per hour are set forth. In the table following the tabular form of conditions and reactants, the product effluent analysis is set forth for each of the feeds of cis-dichloroethylene fed per mole hour.

TABLE THERMAL ISOMERIZATION OF ClS-DICHLOROETHYLENE Reactor Temperature, "C 475 Chlorine Preheater, C 200 RC1 Preheater, C 200 Reactor Pressure, psig 40 Reactor Volume, liter 0.46 Contact Time, sec. 0.6 Feed, mole/hour Chlorine 20.8 1 ,1 -Dichloroethane 9.6 Ethyl Chloride 14.4 cis-Dichloroethylene 0-1 l-2. l I-ICl-Diluent 8.0 cis-Dichloroethylene, 0 1.1 2.1 mole/hour PRODUCT ANALYSIS mole mole mole 7o Ethylene 14.7 14.5 13.6 Vinyl Chloride 20.5 2 l .7 2 l .1 Ethyl Chloride 4.47 2.89 2.55 vinylidene Chloride 6.52 7.84 7.49 trans-Dichlo roethylene 0.55 2.42 4.04 l, l -Dichloroethane 26.4 21.3 20.6 1,1.1-Trichloroethane 22.4 22.5 21.6 cis-Dichloroethylene 0.76 3.37 5.5 l Ethylene Dichloride 1.73 1.70 1.66 Perchloroethylene 0.05 0.09 1.1,2-Trichloroethane 1.67 1.43 1.48 cisztrans 58.0: 58.2: 57.7:

3 4 1. In a method for chlorinating ethyl chloride and TABLE continued 1,1-dich1oroethane to produce 1,1,l-trich1oroethane, THERMAL [SOMERIZATION OF CIS'DICHLOROETHYLENE 1,1-dichloroethane, vinylidene chloride and numerous 42.0 41.8 42.3 by-products and in which process the 1,1-dichloroe- 5 thane is recycled to the chlorination reaction along with cisand trans- 1,2-dich1oroethylene the improve- The following example demonstrates the buildup of ment which comprises separating the trans-1,2- cisand trans-dichloroethane in a chlorination reactor dichloroethylene away from the cis-1,2-dich1oroethyin the commonly employed process wherein the cis-and lene and 1,1-dichloroethane, the recycled cis-1,2- trans-isomers are not removed from association with dichloroethylene being isomerized to an isomeric mixthe 1,1-dich1oroethane which is recycled to the chloriture of about 60% cisand trans-1,2-dich1oroethynation reactor. lene during the chlorination of the 1,1-dich1oroethane RECYCLE OF CIS- AND TRANS-DICHLOROETHYLENES REACTOR TEMPERATURE, C 475 REACTOR PRESSURE, PSIG 40 CHLORINE PREHEAT, C a 200 RC1 PREHEAT, C 200 RUN NO. RUN NO. RUN NO. RUN NO. RUN

NO. FEED, MOLE/HOUR 78 79 80 81 82 CHLORINE 22.8 22.8 22.8 22.8 22.8 ETHYL CHLORIDE I 14.4 14.4 14.4 14.4 14.4 LI-DICHLOROETHANE 9.6 9.6 9.6 9.6 9.6 HYDROGEN CHLORIDE 8.0 8.0 8.0 8.0 8.0 CIS- AND 0 0.6 1.2 2.4 4.8 TRANS-DICHLOROETHYLENE *CIS-AND 0 2.5 5.0 10.0 20.0 TRANS-DICHLOROEI'HYLENE,

MOLE

REACTOR EFFLUENT MOLE MOLE MOLE 7a MOLE MOLE EI'HYLENE 12.78 12.69 10.29 10.02 7.68 VINYL CHLORIDE 26.39 25.77 25.59 22.89 17.96 ETHYL CHLORIDE 1.14 1.15 0.59 0.79 0.65 VINYLIDENE CHLORIDE 13.08 12.53 16.39 13.41 10.84 TRANS-DICHLOROETHYLENE 1.25 2.25 3.77 5.42 7.80 1,1-DICHLOROETHANE 14.81 14.53 9.87 11.60 11.14 1,1,1-TRICHLOROETHANE 23.96 23.23 21.95 21.65 22.78 CIS-DICHLOROETHYLENE 2.13 3.85 6.13 8.61 12.62 TRICI-ILOROETHYLENE 0.93 1.02 1.87 2.00 2.63 EI'HYLENE DICHLORIDE 0.86 0.96 0.90 0.90 0.90 PERCHLOROETHYLENE 0.08 0.08 0.25 0.20 1.08 1,1,2-TRICHLOROETHYLENE 1.76 1.44 1.50 1.56 2.56 UNSYM-TETRACHLOROETHANE 0.84 0.50 0.87 0.95 1.61 CIS- AND 3.38 6.10 9.90 14.03 20.42 TRANS-DICHLOROETHYLENE AClS- AND 2.72 6.52 10.65 17.04

TRANS-DICHLOROETHYLENE "Based on moles RC1 fed.

and ethyl chloride. We claim: 

1. IN A METHOD FOR CHLORINATING ETHYL CHLORIDE AND 1,1DICHLOROETHANE TO PRODUCE 1,1,1-TRICHLOROETHANE, 1,1DICHLOROETHANE, VINYLIDENE CHLORIDE AND NUMEROUS BY-PRODUCTS AND IN WHICH PROCESS THE 1,1-DICHLOROETHANE IS RECYCLED TO THE CHLORINATION REACTION ALONG WITH CIS- AND TRANS- 1,2DICHLOROETHYLENE THE IMPROVEMENT WHICH COMPRISES SEPARATING THE TRANS-1,2-DICHLOROETHYLENE AWAY FROM THE CIS-1,2DICHLOROETHYLENE AND 1,1-DICHLOROETHANE, THE RECYCLED CIS1,2-DICHLOROETHYLENE BEING ISOMERIZED TO AN ISOMERIC MIXTURE OF ABOUT 60% CIS- AND 40% TRANS- 1,2-DICHLOROETHYLENE DURING THE CHLORINATION OF THE 1,1-DICHLOROETHANE AND ETHYL CHLORIDE. 